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cows eating grass

Sources of Excess Sulfur


In many areas of the United States, surface and deep waters are high in sulfate. Sulfate salts precipitate where evaporation of high sulfate water occurs. Water sulfate concentrations can increase as water evaporates in hot weather.

Water consumption by cattle is temperature dependent and increases greatly at high temperatures. Therefore, in hot weather, sulfur intake from water can be elevated due to concurrent increases in water consumption and sulfate concentrations in water.


High protein forage such as alfalfa can serve as a source of sulfur, probably as a consequence of the sulfur-containing amino acid content of the protein.

It has been shown that rumen microbes incubated ex-vivo can generate H2S from added cysteine and methionine. These sources can make important contributions to the total sulfur intake.

In general, grasses tend to be low in sulfur, likely as a consequence of their low protein content. However, under some circumstances grasses can be high in sulfate. Certain weeds seem to be able to accumulate large amounts of sulfate. These include Canada thistle (Cirsium arvense), kochia (Kochia scoparia), and lambsquarter (Chenopodium spp.). These sources can make important contributions to total sulfur intake of ruminants. More needs to be learned about the factors that govern the accumulation of sulfate in plants so that the occurrence of hazardous conditions can be better understood and predicted.

Cruciferous plants constitutively produce glucosinolates, which have 2 sulfur atoms per molecule. Cruciferous forages serve as important sources of sulfur and have been associated with outbreaks of PEM.

Co-products of corn, sugar cane, and sugar beet processing commonly have high sulfur content. This is due to the addition of sulfur-containing acidifying agents. PEM has been associated with the use of these types of co-products as feed ingredients. A high molasses-urea diet has been associated with a form of PEM. It is likely that this represents a type of sulfur-related PEM due to the high sulfur content of the molasses. Similar scenarios are likely with beet and corn co-products, although careful analyses have not been done.

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